Alkali-silica reaction (ASR) was first identified as a form of concrete deterioration in the late 1930s (Stanton 1940). Approximately I0 years later, it was discovered that lithium compounds can he used to control expansion due to ASR. There has recently been increased interest in using lithium technologies to both control ASR in new concrete arid to retard the reaction in existing ASR-affected structures. This facts book provides information on lithium, its origin and properties, and on its applications. The mechanism of alkali-silica reaction is discussed together with methods of testing to identify potentially alkali-silica reactive aggregates. Traditional methods fix minimizing the risk of damaging ASR are presented; these include the avoidance of reactive aggregates, controlling the levels of alkali in concrete and using supplementary cementing materials such as fly ash, slag and silica fume. The final two sections of 'this facts book discuss the use of lithium first as an admixture for new concrete construction and second as a treatment for existing concrete structures affected by ASR.